The need of finding a new way of working the coal mines of England, and of marketing the coal, which had been such an important factor in the development of the steam-engine, was a scarcely less important factor in the building of the earliest practical railway locomotive. The coal had to be hauled from the pit of the colliery to the shipping place. It was carried in cars that were pushed or pulled over a rude line of wooden or iron rails. But it was evident from the time when James Watt began to build his steam-engines to lift the coal from the mine that men of inventive minds would soon seek to send the cars over the level ground by the same power. We owe the railroad chiefly to the needs of the north of England, and there we find the real birth of the locomotive. About the beginning of the nineteenth century a number of men in England were experimenting with new means of locomotion, both for merchandise and for passengers. Their projects varied from cars running on wheels and drawn by horses to carriages propelled by small stationary steam-engines, placed at short distances from each other along the road. In 1802 Richard Trevethick, a captain in a Cornish tin-mine, took out a patent for a steam-carriage. The machine he built looked like an ordinary stage-coach on four wheels. It had one horizontal cylinder, which was placed in the rear of the hind axle, together with the boiler and the furnace-box. The motion of the piston was carried to a separate crank-axle, and that in turn gave the motion to the axle of the driving-wheel. This was in itself a great invention, being the first really successful high-pressure engine that was built on the principle of moving a piston by the elasticity of steam against only the pressure of the air. The steam was admitted from the boiler under the piston that moved in a cylinder, and forced it upward. When the motion had reached its limit, the communication between the piston and the under side of the cylinder was shut off, and the steam escaped into the atmosphere. Then a passage was opened between the boiler and the upper end of the piston, which was consequently pushed downward, and then the steam was again allowed to escape. As a result the power of the engine was equal to the difference between the atmosphere’s pressure and the elastic force of the steam in the boiler. This steam-carriage of Trevethick was fairly successful, and created a great sensation in that part of Cornwall where it was built. He decided to take it to London, and drove it himself to Plymouth, from which port it was to be carried by sea. On the road it caused amazement and consternation, and won the name of Captain Trevethick’s dragon. He exhibited it in London, but after a short time gave up driving it, believing that the roads of England were too badly built to make the use of a steam-carriage feasible.